Late Subscriber Py

test_late_sub.py

import rclpy
from rclpy.executors import SingleThreadedExecutor
from rclpy.qos import QoSDurabilityPolicy
from rclpy.qos import QoSProfile
from rclpy.qos import QoSReliabilityPolicy
from std_msgs.msg import String

def main(args=None):
    topic = 'TOPIC'
    topic_type = String
    
    rclpy.init(args=args)
    qos_profile = QoSProfile(
        depth=parsed_args.history,
        # Guaranteed delivery is needed to send messages to late-joining subscription.
        reliability=QoSReliabilityPolicy.RELIABLE,
        # Store messages on the publisher so that they can be affected by Lifespan
        durability=QoSDurabilityPolicy.TRANSIENT_LOCAL)
    node = rclpy.node.Node('listener')
    sub = node.create_subscription(
        String,
        topic,
        topic_type,
        lambda msg: print(msg),
        qos_profile)
    rclpy.spin(node)
    rclpy.shutdown()

if __name__ == "__main__":
    main()